Sight

What are the two ways light can be conceptualized and what is the difference?

-As waves for when it moves around the world

-As photons when they are being absorbed

What is a photon?

a quantum of visible light or other form of electromagnetic radiation demonstrating both particle and wave properties

What is the spectrum of visible light?

400-700 nm

What is the cornea?

transparent window of the eyeball. It has no blood or blood vessels, but has a rich supply of sensory nerve endings.

What is the aqueous humor?

fluid derived from blood that fills the space immediately behind the cornea. It supplies oxygen and nutrients and removes waste from the cornea and the crystalline lens.

What is the crystalline lens?

The lens inside the eyeball that enables change of focus.

What is the pupil?

The dark circular opening at the center of the iris in the eye where light enters.

What is the iris?

The colored part of the eye. It has a muscular diaphragm surrounding the pupil that regulates the light that enters the eye by expanding and contracting the pupil.

What is the vitreous humor?

the transparent fluid that fills the vitreous chamber in posterior part of the eye.

What is the retina?

mebrane that receives image from lens, and sends it to the brain via the optic nerve. It is where seeing begins.

What is accommodation?

process where eye changes its focus in which lens gets fatters as gaze is directed toward nearer objects.

What is Presbyopia? How does it occur?

"old sight" loss of near vision because of insufficient accomadiation. We begin to lose our ability to accomadate as we age because the lens becomes harder and the capsule around it loses its elasticity.

What is a cataract? When do they usually occur?

opacity of the crystalline lens. Most occur after the age of 50 but there are rare cases on congenital cataracts which occurs at birth.

What emmetropia?

No refractive error, because the refractive power matches perfectly to the length of the eyeball.

What is myopia?

nearsightedness, Condition where eyeball is too long, object is focused in FRONT of the retina and distant object can't be seen sharply. Corrected with negative lenses.

What is hyperopia?

farsightedness, light is focused behind retina.

What is astigmatism?

Curving of one or more refractive surface of the eye, usually the cornea.

What is the fundus?

the back layer of a patient's eye.

What is the optic disc?

White cirlce on the fundus, This where arteries and veins that feed the retina enter, and where axons of the ganglion cells leave

What are photoreceptors? Distinguish between the two types.

Photoreceptors are light sensitive receptors in the retina. The two types are rods and cones. Rods are specialized for night vision, while cones are for day-light vision, fine visual acuity, and color. Rods have one type of photopigment, rhodopsin. Cones have photopigments that are short, medium, or long.